The practice of forming pneumatic vehicle tires with a tread profile in which radially raised profile elements are spaced apart by grooves is known. In this case, the tread profiles are formed with a profile depth optimized for the respective use. In this case, the grooves are formed with the maximum profile depth to the maximum extent over most of the area of extent thereof.
The practice of forming the tread profile in a manner optimized for the use, including a profile depth set in an optimized way for this purpose, is known in the case of pneumatic tires for commercial vehicles. Many commercial vehicle tires are formed from circumferential grooves extending over the circumference of the tire and from circumferential ribs separated from said grooves or profile block rows extending over the circumference, wherein the relatively wide circumferential grooves are formed with a maximum profile depth across the circumference over most of the area of extent thereof.
Another known practice in the case of pneumatic commercial vehicle tires of this kind is to form the tread with an additional thickness of material to prolong the life of the tire, with the result that there is a relatively large amount of rubber material between the belt of the commercial vehicle tire and the tire surface, including below the groove bottom of the circumferential grooves. The profile depth determined for the optimum use of a new tire is maintained by constructing it with the conventionally optimized profile and the maximum profile depth suitable therefor. As soon as the tread profile has worn down to such an extent that the required minimum profile depth remains, the profile of pneumatic commercial vehicle tires of this kind can be regrooved once more. The suitability for regrooving is indicated on the commercial vehicle tire.
For regrooving, the pneumatic commercial vehicle tires are removed from the vehicle and regrooved manually using special regrooving tools. For this purpose, the person performing the regrooving must in each case use a regrooving tool suitable for the respective regroove, this being selected in accordance with the respective groove shape. The special regrooving tool is inserted into the groove and drawn across the circumference of the pneumatic commercial vehicle tire, thereby removing rubber material from the lower groove base and from the lower groove flank region and leaving deepened grooves. For this purpose, the person performing the regrooving must set the penetration depth with a high accuracy and keep it as constant as possible. If the penetration depth is too small, the use of the pneumatic commercial vehicle tire is prolonged only slightly. To achieve accurate shaping of the desired recut circumferential groove, the special dies for regrooving furthermore require a minimum regrooving depth. If the regrooving depth selected is too small, this has a negative effect on the recut cross-sectional contour of the circumferential groove. Excessively deep regrooving can limit the durability and utility of the regrooved tire in an unwanted way. High accuracy in the regrooving depth to be maintained is therefore especially important. Achieving an optimum penetration depth and keeping it constant during cutting therefore involves a lot of effort for the person performing the regrooving.
One proposal already made in the context of a tread profile of this kind on a pneumatic commercial vehicle tire is to form, in the groove base of the circumferential groove, a circular-cylindrical depression similar to a bore which is delimited in the radial direction by a depression base, wherein the depression base is formed at the depth, measured from the groove base, intended to correspond to the regrooving depth. In this regrooving indicator, the depression base is therefore configured as a measure of the regrooving depth to be set and maintained. For regrooving, the person performing the regrooving takes the appropriate regrooving tool for the shape of the circumferential groove and for the regrooving depth to be cut and recuts the circumferential groove. The only reference point for monitoring and maintaining the regroove is the depression base. The person performing the regrooving does therefore admittedly have clear information on whether they have not yet reached the desired regrooving depth or whether they have already reached it. However, they do not have any information on whether they have just reached the regrooving depth indicated in the tire, have already exceeded it slightly or have already significantly exceeded it, necessitating rejection. The accuracy of regrooving is thus still limited and very dependent on the individual manner of approach of the person performing the regrooving. In order to ensure high accuracy in the regrooving quality, a lot of additional effort and very carefully monitored regrooving work is thus required.
It has sometimes also been proposed to impart information on the regrooving work with the aid of fine indents in the groove base. However, simply using fine indents in the groove base as regrooving indicators does not allow simple optical premeasurement of the regrooving depth that is actually possible for the respective circumferential groove, this premeasurement understandably being desired and generally being carried out with conventional depth measuring equipment by the person performing the manual regrooving. Here, the person performing the regrooving would have to rely completely on general information available to them without themselves checking beforehand the regrooving depth that would actually be correct for the respective regrooving operation on the tire at hand. With their simple optical measuring instruments, they cannot check quickly and easily whether the regrooving depth that actually remains corresponds to assumptions, possibly owing to damage or incorrect handling. For this purpose, the person performing the regrooving would have to acquire and employ special measuring devices and measuring methods which go beyond a purely visual check.